The use of an indirect-fed antenna has a number of benefits and the discussion of this technology is provided in PCT Application No. PCT/US 10/4797, filed Sep. 7, 2010, which is incorporated herein by reference in its entirety. FIG. 1 illustrates an exemplary design that can be used to provide such a system. A low band antenna 30 includes a feed 31 that is coupled to a coupler 32. The coupler 32 couples with a high-band element 35 that has a short 37 that couples to the high-band element 35 to ground. A high-band antenna 40 includes feed that is coupled to slot 42, which has a short 47 to ground. A high-band element 45 capacitively couples to the slot 42 and has a short 48 to ground. Both the low-band and high-band antennas can be configured with the appropriate components so as to ensure the frequency response is appropriate. For example, an inductor or capacitor can be place in series with the coupler to adjust the impedance of the low band antenna. In addition, an inductor can be place in series between the high-band element and the ground to adjust the impedance of the high band antenna.
An impedance plot of the Low Band HISF antenna is shown in FIG. 2A for the raw antenna and in FIG. 2B when matched to 50Ω. As can be appreciated from FIGS. 2A and 2B, a low-band frequency range 51, which can extend from a starting value 51a (which can be a lower end of GSM 850) to an ending value 51b (which can be an upper end of GSM 900) is shifted into a desired position on the Smith chart with the use of the appropriate components (e.g., the addition of an inductor or capacitor between the feed and coupler) so that the response over the low-band frequency 51 is within a standing wave ratio (SWR) circle 55, which can have a value of 3.
An impedance plot of the High Band LISF antenna is shown in FIG. 3A for the raw antenna and in FIG. 3B for an antenna matched to 50Ω. As can be appreciated from FIGS. 3A and 3B, a high-band frequency range 52, which can extend from a starting value 52a (which can be a lower end of GSM 1800) to an ending value 52b (which can be an upper end of UMTS 1 (Rx) is shifted into a desired position on the Smith chart so that the response over the high-band frequency 52 is within the SWR circle 55.
While the depicted system is relatively compact, pressure to make mobile devices smaller and more energy efficient while at the same time increase performance has created increased pressure on the communication system. Chip designers are integrating multiple communication chipsets into CPU designs in an attempt to maximize efficiency and performance. Developing an antenna system that could somehow enhance the communication system performance would therefore be appreciated by certain individuals.